Theory of Operation

The resistance of a conductor can be expressed as:

(1)     

where:

R is the resistance,

is the material resistivity,

L is the length of the conductor, and

A is the cross-sectional area of the conductor.

It can be shown that the change in resistance of a conductor is linearly related to the strain by:

(2)     

where:

[[epsilon]]axial is the axial strain (m/m),

F is the sensitivity of the strain gauge (gauge factor), and

R is the change in resistance.

In most cases, the values of F and R are provided by the manufacturer, and the user measures [[Delta]]R to determine the strain.

Since the typical change in resistance of a strain gauge is extremely small (~0.00024 ), sensitive instrumentation is required to measure the strain.